a) Field of the Invention
The present invention relates to a manufacturing method and apparatus for an optical disc having a plurality of recording layer surfaces.
b) Description of the Related Art
Recently, such a high density recording medium as an optical disc called a digital versatile disc (hereinafter, abbreviated as DVD) has been developed as a product of a technique which increases a recording capacity on recording surfaces.
Furthermore, there is an increasing tendency on the recording capacity of the optical disc to highly densify the recording capacity. For example, in a four-layer recording structure, the optical disc called DVD-18 on which a recording has been made for each of two layers thereof from both surfaces has the recording capacity of 17 GB (Gigabytes).
Japanese Patent Application First (unexamined) Publication No. Heisei 10-283682 published on Oct. 23, 1998 and Japanese Patent Application Second (examined) Publication No. Heisei 8-23941 published on Mar. 6, 1996 exemplify previously proposed manufacturing methods of the multi-layer optical discs such as the DVD-18 as described above.
In each of the previously proposed manufacturing methods described in the above-described Japanese Patent Application Publications, manufacturing steps of either of its recording surfaces include: a step of peeling off an interface between a stamper and an adhesive layer, the stamper being used for each layer, a step of transcribing the information recorded by means of pit rows on the adhesive layer formed on the interface; and a step of forming a reflective film on the adhesive layer.
Since, in the previously proposed manufacturing method, the steps using the stamper by plural number of times are continued serially, a time length of the whole manufacturing steps (in a whole manufacturing line) is accordingly extended.
In addition, it is necessary to carry out strict control over the steps using the stamper in a clean room. It is not always efficient to provide the steps using the stamper alternately with steps of bonding mutually the layers which are different in qualities.
It is, therefore, an object of the present invention to provide an improved manufacturing method and apparatus for the optical disc in which no stamper is used and a step of forming a reflective film on an adhesive layer after the step of transcribing the information is deleted and which are appropriate for a mass production of the optical disc.
According to one aspect of the present invention, there is provided with a method for manufacturing an optical disc, comprising: bonding a transparent disc substrate having two relatively wide-area surfaces thereof on at least one of which a first information is recorded and a first reflective film is formed onto a dummy disc having the similar relatively wide-area surfaces thereof on at least one which a second information is recorded and a second reflective film is formed via an adhesive layer; and applying an external force between the dummy disc and the disc substrate through an integrated center hole penetrated through the dummy disc and the disc substrate at center positions thereof to peel off the dummy disc at a first interface between the dummy disc and the second reflective film thereof.
According to another aspect of the present invention, there is provided with an apparatus for manufacturing an optical disc comprising: a bonding device to bond a transparent disc substrate having two relatively wide-area surfaces thereof on at least one of which a first information is recorded and a first reflective film is formed onto a dummy disc having the similar relatively wide-area surfaces thereof on at least one of which a second information is recorded and a second reflective film is formed via an adhesive layer; and an external force applying device to apply an external force between the dummy disc and the disc substrate through an integrated center hole penetrated through the dummy disc and the disc substrate at center positions thereof to peel off the dummy disc at a first interface between the dummy disc and the second reflective film thereof.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.